Microcapsule synthesis

Figure 8.1 Nano- and microcapsule synthesis (a) coacervation, (b) interfacial polymerization, (c) colloidosomes, (d) colloidal templating, and (e, f) vesicles.

Priest C, Quinn A, Postma A et al (2008) Microfluidic polymer multilayer adsorption on liquid crystal droplets for microcapsule synthesis. Lab Chip 8(12) 2182-2187... 

Microcapsules are micron-sized particles with a hollow interior that can enclose active ingredients such as drugs. Microfluidics is widely used in the synthesis of microcapsules to achieve homogeneous size. A typical microfluidic system for microcapsule synthesis may involve injection of the polymer precursor or monomer through a first... 

Sakai, S., Ono, T., Ijima, H. and Kawakami, K. (2001) Synthesis and transport characterization of alginate/ aminopropylsilicate/alginate microcapsule application to bioartificial pancreas. Biomaterials, 22, 2827-2834. 

The pore size and distribution in the porous particles play essential roles in NPS synthesis. For example, only hollow capsules are obtained when MS spheres with only small mesopores (<3 nm) are used as the templates [69]. This suggests that the PE has difficulty infiltrating mesopores in this size range, and is primarily restricted to the surface of the spheres. The density and homogeneity of the pores in the sacrificial particles is also important to prepare intact NPSs. In a separate study, employing CaC03 microparticles with radial channel-like pore structures (surface area 8.8 m2 g 1) as sacrificial templates resulted in PE microcapsules that collapse when dried, which is in stark contrast to the free-standing NPSs described above [64]. 

Our research group has developed a multicatalyst system around an encapsulated amine catalyst (Kobaslija and McQuade 2006) that promotes nitroaUcene synthesis. Like the Royer catalysts, these microcapsules are based on a PEI shell. Unlike that system, however, templating is accomplished with a methanol in cyclohexane ( oil-in-oil ) emulsion in an interfacial polymerization, with the PEI cross-linked... 

Polythiophenes, with ferrocene groups, 12, 305 Polyurea microcapsules, Pd-containing, 12, 713-714 Poly(vinylcymantrene), synthesis, 12, 311 Poly(vinylferrocene), preparation and properties, 12, 301 Polyynes... 

Bachtsi, A.R. Kiparissides, C. Synthesis and release studies of oil-containing poly(vinyl alcohol) microcapsules prepared by coacervation. J. Controlled Release 1996, 38 (1), 49-58. 

In an early study by Lin et al., insulin-loaded polylactic acid (PLA) microcapsules were synthesized by an emulsification-solvent evaporation process originally reported by Beck et al. Several parameters in the synthesis process were modified with the intention of optimizing the insulin release profile. Such modifications included variations in types, concentrations, and viscosities of protective colloids used in the emulsification process. Polyvinyl alcohol (PVA), when used as the protective colloid in the fabrication process, was found to produce the PLA microparticles in reproducible quality. Further studies revealed that the concentration PVA directly affects the PLA particle size and the surface characteristics of the microcapsules. With higher concentrations of PVA, microparticles tended to be smaller and to have a smoother surface. When the release profiles of the microcapsules were stud-... 

Yu J, Murthy VS, Rana RK, Wong MS (2006) Synthesis of nanoparticle-assembled tin ox-ide/polymer microcapsules. Chem Commun 10 1097-1099... 

Hong, K., Park, S., 1999. Melamine resin microcapsules containing fragrant oil synthesis and characterization. Materials Chemistry and Physics 58 (2), 128—131. 

R.V. Parthasarathy and C.R. Martin, Synthesis of polymeric microcapsule arrays and their use for enzyme immobilization. Nature, 369(6478), 298-301 (1994). 

Zengliang, C. Yuling, R Zhongning, Z. Synthesis and assessment of attractiveness and mating disruption efficacy of sex pheromone microcapsules for the diamondback moth, Plutella Xylostella (L). Chinese Science Bullettin 57(10), 1365-1371, 2007. 

Scarfato, P. Avallone, E. lannelli, R De Eeo, V. Acierno, D. Synthesis and characterization of polyurea microcapsules containing essential oils with antigerminative activity. Journal of Applied Polymer Science (2007), 105(6), 3568-3577. 

Reed, J. L. McFarland, B. H. Synthesis of microcapsules containing dialkylanilines and their use in frontal polymerization. Ahstracts of Papers, 235th ACS National Meeting, New Orleans, LA, April... 

Lu, J. Pan, J. Chen, S. Hua, Z. Synthesis and properties of pressure-sensitive color— Developing microcapsule—Effects of the dosage of system modifier and the pH of microcapsule slurry on the properties of microcapsule. Zhongguo Fangzhi Daxue Xuebao (1998), 24(1), 5-8. 

Wang, W. Xu, L. Liu, R Li, X. Xing, L. Synthesis of isocyanate microcapsules and micromechanical behavior improvement of microcapsule shells by oxygen plasma treated carbon nanotubes. Journal of Materials Chemistry A Materials for Energy and Sustainability (2013), 1(3), 776-782. 

Boh B., Staresinic M., and Sumiga B., October 5-8, 2011. Synthesis and applications of scented microcapsules in textile products. XIX International Conference on Bioencapsulation, Amboisc, Fiance. 

Podshivalov, A. V., Bronnikov, S., Zuev, V. V., Jiamrungraksa, T., and Charuchinda, S. (2013). Synthesis and characterization of polyurethane-urea microcapsules containing galangal essential oil Statistical analysis of encapsulation. Jourrwl of Microencapsulation, 30,198-203. 

Application ultrasound has been used for the synthesis of materials, coating carbon nanotubes and noble metals, destruction and fragmentation of contrast agents, gas release, polymer destruction, and in drug delivery. i Ultrasound application has effect on permeability of PEC microcapsules. 

The formation of microcapsules is greatly affected by the surfactant, which influences not only the mean diameter but also the stability of the dispersion. The surfactants used in the system have two roles, the first one to reduce the interfacial tension between oil and aqueous phases allowing formation of smaller microcapsules and the other one to prevent coalescence by its adsorption on the oil-water interface and therefore by forming a layer around the oil droplets. The synthesis of a core/ shell particle or other possible morphologies is mainly governed by the kinetic factors and thermodynamic factors. 

Ma, Y Chu. X. Tang, G. Yao, Y. Synthesis and thermal properties of acrylate-based polymer shell microcapsules with binary core as phase change materials. Mater Lett 91 (2013) 133—135. 

Alay, S. Alkan, C. Gode, F. Synthesis and characterization of poly(methylmethacrylate)/n-hexadecane microcapsules using different cross-linkers and their application to some fabrics. Thermochim Acta 518 (2011) 1-8. 

Chen, Z. Cao, L. Fang, G. Shan, F. Synthesis and characterization of microencapsulated paraffin microcapsules as shape-stabilized thermal energy storage materials. Nanosc Microsce Therm 17(2)... 

Pascu, O. Garcia-Valls, R. Giamberini, M. Interfacial polymerization of an epoxy resin and carboxylic acids for the synthesis of microcapsules. Poly Int 57 (2008) 995-1006. 

Borreguero, A.M. Valverde, J.L. Rodriguez, J.F. Barber, A.H. Cubillo, J.J. Carmona, M. Synthesis and characterization of microcapsules containing Rubitherm RT27 obtained by spray drying. Chem Eng J166 (2011) 384-390. 

Amphiphilic ABA-type triblock copolymers containing PDMS, two poly(2-methyl-oxazoline) -PMOXA- side blocks and methacrylate terminal groups have a eomplex selfassembling behavior, which allows for the synthesis of covalently cross-linked hydrogels, with applications as contact lenses [106]. Cross-linked vesicles of such polymers are nano-and microcapsules which act as stable nanoreactors with controlled permeability [107-109]. 

Nesterova, T., Dam-Johansen, K., and Kill, S. Synthesis of durable microcapsules for self-healing anticorrosive coatings a comparison of selected methods. Progress in Oiganic Coatings, 70(4), 342-352 (2011). 

There are a variety of different types of particle that can be synthesized using microfluidics and the exact fluidic format used defines the flow characteristics of the synthesis environment which needs to be carefully matched to the synthetic requirements of each particle type. Broadly speaking, the main particle types of interest include monodisperse microgels, metal nanoparticles and nanocrystals, core-shell particles, microemulsions, and microcapsules. Typically these particles should be homogeneous in size and are composed either of an organic polymer matrix or a metal or metal mixture at the micron or nanometer scale. In addition to these simple particle architectures, we may also consider more complex particles composed of multiple layers or components such as core-shell particles or using a central cavity to encapsulate small molecules, proteins, or other particles, and these are called microcapsules. 

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